The application relates to systems for viewing stereoscopic 3-D images. More specifically, this application relates to a system for providing stereoscopic 3-D vision with full 3-D depth sensation.
To further understand the invention, a short introduction concerning 2-D video displays follows. Diverse types of image display devices have been developed for displaying 2-D images. Examples of such technologies include: cathode ray tube (CRT) display monitors; liquid crystal display panels; plasma display panels; active-matrix plasma display panels, etc. Presently, the CRT display device (i.e., CRT tube) is widely used in most video monitors of personal computer (PC) systems, as well as in most commercially produced television sets. The principle difference between a CRT computer video monitor and a CRT television display tube is the rate at which image frames or lines are displayed, and the composition of the video signals which each such display device is designed to receive and display during the image display process. In conventional CRT-based television sets, which are constructed and operate according to NTSC or PAL design criteria, the horizontal and vertical synchronization (or retrace) signals are multiplexed with the RGB (i.e., color) signals to produce a single composite video signal that is transmitted over a signal conductor.
In conventional CRT-based computer display monitors, which are constructed and operated according to VGA or SVGA design criteria, the horizontal synchronization signal, and the RGB (i.e., color) signals are each transmitted separately over individual signal conductors and require a six (6) pin electrical connector for VGA and SVGA styled video monitors.
These design standards create different electrical interface requirements for such types of CRT display devices. NTSC and PAL video signals can only be driven by NTSC and PAL signals, respectively, whereas VGA and SVGA styled video display monitor devices can only be driven by VGA and SVGA video signals, respectively. Therefore, VGA or SVGA video signals generated from a graphics accelerator/video board within a computer graphics workstation cannot be used to produce video graphics on a CRT-based television set without the use of special signal conversion equipment. Similarly, NTSC or PAL video signals generated from a television set or VCR player cannot be used to produce video graphics on a CRT-based computer video monitor without the use of similar special signal conversion computer.
While there exist several different techniques for achieving stereoscopic 3-D viewing with depth sensation, the “field-sequential” or “time-multiplexing” technique enjoys great popularity. The field-sequential technique sequentially presents to the left eye of a viewer the left image of a stereoscopic image pair displayed on a video display screen during a left image display period, and thereafter, presents to the right eye of the viewer the right image of the stereo pair displayed during a right image display period.
In one known implementation, the field-sequential system uses LCD shutter glasses to control the image presented to the viewer. More specifically, the function of the LCD shutters is to sequentially change optical state during the left and right image display periods, in order to allow the viewer to sequentially undergo a change in his viewing from left eye to right eye and vice versa. This allows the viewer to view displayed stereo pairs in a manner which produces simulated 3-D viewing. Simulated 3-D viewing is produced because the left and right images are fused in the mind of the viewer into one image.
The function of the shutters is implemented by electrically switching the optical state of the LCD shutters in response to trigger signals. In particular, at the beginning of the left image display period, the optical state of the left eye LCD shutter is synchronously switched from its opaque state to its transparent state and the optical state of the right eye LCD shutter is synchronously switched from its transparent state to its opaque state. At the beginning of the right image display period, the optical state of the right eye LCD shutter is synchronously changed from its opaque state to its transparent state and the optical state of the left eye LCD shutter is synchronously changed from its transparent state to its opaque state.
Two specific platforms upon which the time-sequential technique can be provided are platforms providing interlaced (or interleaved) images and platforms providing page-flipped non-interleaved (or progressive) images.
The interlacing method uses the interlaced mode of the display device, wherein the odd lines of an image buffer are displayed in one vertical sweep (which corresponds to a complete screen image) of the cathode ray or other suitable image producer, while the even lines of the image buffer are displayed during the next vertical sweep. In the interlaced mode, the two image streams are interleaved by placing one image stream on the odd lines of the buffer, and one image stream on the even lines, which produces a single interleaved image stream. The interleaved image stream is then converted to a time multiplexed pair of image streams by the interlacing hardware of the display device. This produces an image which, with the aid of synchronized shutter glasses, appears to the viewer in 3-D.
In the page-flipped mode, the time-multiplexing involves alternately displaying images from two image streams. This is accomplished by either copying them one after another into a single image buffer, or by copying them into two separate image buffers and then rapidly switching the display device between the two buffers.
Presently, a number of line blanker systems which utilize specialized display devices are available for use with the field-sequential stereoscopic 3-D image display technique. While some systems are designed for use with CRT display devices driven by VGA video signals (which have an interlaced and a non-interlaced mode), others are designed for use with CRT display devices driven by composite video sources (which have only an interlaced mode).
One drawback of conventional line blanker systems involves an inability to identify the first line of video in a video image. An undetermined first line can cause some video resolutions to be displayed in pseudostereoscopic format (that is, the right and left images are displayed to the wrong eyes because the line-blanking is out of phase with the shutter glasses).
Another drawback of conventional line blanker systems is the inability to enable or disable the blanking feature. It may be desirable to turn off the line blanking when 2-D images and text information are to be viewed on the display.
Another drawback of conventional line blanker systems is that line blanking is typically accomplished by replacing video lines with “black” (or non-viewable) information. This method cuts the resolution and brightness of the line-blanked image by a factor of two.
Therefore, it would be desirable to provide a line blanker system that can identify the first line of a video image.
It would also be desirable to provide a line blanker system that is capable of enabling and disabling the line blanking feature.
It would also be desirable to provide a line blanker system that allows a video image to be viewed with full resolution and brightness.